An investigation by the US Environmental Protection Agency at a site in …

Making the link

On Thursday, the EPA released a draft of its report on the investigation, which is available on the project website. The report's conclusions are sure to stir up the debate, as it draws a pretty strong connection between fracking and groundwater contamination in Pavillion. The report will go through public comment and peer review by an independent panel of scientists before being finalized, but it seems unlikely the conclusions will change much given the multiple lines of evidence that support them.

Concerning the waste fluid pits, the report concludes they are clearly a source of shallow groundwater contamination. Benzene, for example, was detected in groundwater samples collected near the pits at concentrations 78 times the health standard. There are at least 33 of those waste fluid pits in the Pavillion area, three of which have been investigated and are currently being remediated by Encana in cooperation with the Wyoming Department of Environmental Quality.

The report really starts to get interesting when it comes to the pair of deep monitoring wells that the EPA installed in 2010. All kinds of compounds had shown up in the groundwater taken from those wells, including petroleum compounds (such as benzene, toluene, ethylbenzene, xylenes, and naphthalene), methane, and known fracking fluid chemicals like 2-butoxyethanol. When asked about the results from those monitoring wells, an Encana representative told Ars, "These were drilled into known gas-bearing zones. Given this, the results (high levels of methane and petroleum-related hydrocarbons) are not surprising. On the other hand, sampling of private drinking water wells found no oil and gas related compounds exceeding state or federal drinking water standards."

The EPA report, however, indicates that these compounds were present. It concludes that "the explanation best fitting the data for the deep monitoring wells is that constituents associated with hydraulic fracturing have been released into the Wind River drinking water aquifer at depths above the current production zone."

This is based on several lines of evidence. First, the pH of water from the wells is "unusual and unexpected," measuring 11.2-12. That's much higher than domestic well water or measurements reported elsewhere in the aquifer.

Beyond that, the character of the alkalinity is very strange. Instead of high concentrations of carbonate and bicarbonate (as would normally be the case), the alkalinity is almost entirely due to hydroxide ions. This implies that the high pH is due to the addition of a strong base rather than to natural conditions. As it turns out, potassium hydroxide is a common component in fracking fluids.

Along the same lines, potassium and chloride concentrations are extremely high—much higher than in shallower wells. That's unusual because concentrations of those elements normally decrease with depth in this region.

The report also argues that the petroleum compounds detected (at high concentrations) in the monitoring wells are unlikely to come from natural sources. Pockets of natural gas in the area are not known to be associated with long-chain condensates. In addition, while concentrations of methane in the two wells are similar, the concentrations of other hydrocarbons are significantly different.

More importantly, several synthetic and unusual compounds were detected, including 2-butoxyethanol, isopropanol, and a few glycols—all of which are known to be used in fracking fluids. Another compound, tert-butyl alcohol (TBA), is a breakdown component of a couple different potential fracking components, including the gasoline additive MTBE.

Geology and drill sites

The report makes some striking comments about the geology of the site as well. Rather than the classic picture of fracking operations separated from drinking water aquifers by many thick, impermeable layers, a much different judgment of the stratigraphy is given. The EPA reports that there is "no lithologic barrier (laterally continuous shale units) to stop upward vertical migration of aqueous constituents of hydraulic fracturing." This leads to a pair of critical statements: "The Wind River Formation meets the definition of an Underground Source of Drinking Water under the United States Code of Federal Regulations… Fluids used for hydraulic fracturing were injected directly into the Wind River Formation."

Given that fact, it seems that the injection of fracking fluids at Pavillion should not have been exempt from regulation under the Safe Drinking Water Act. That challenges the categorical exception given to fracking operations by the 2005 Energy Policy Act.

More surprises come in the analysis of the cement seals around gas well casings. The EPA obtained records of cement seal integrity logs that were made using an acoustic geophysical tool that was lowered down some of the wells. While it's not the greatest data, it's still a useful indicator of how good the cement seal between the casing pipe and borehole wall actually is. The logs showed that intervals of "sporadic bonding" were common, including some directly above the elevations where fracking had taken place. Incredibly, two of the well logs showed no cement at all for the first 600 to 800 meters below the ground surface.

Several lines of evidence were also used to draw a likely connection between gas production and the natural gas in domestic water wells. The report cites several reasons for making that connection: the chemical and isotopic composition of the gas; the correlation between gas concentrations in water wells and proximity to active gas production wells; and the fact that so many residents experienced issues soon after fracking began.

It also cites the remarkable case (recounted in Gasland) of one homeowner's attempt to replace a water well that turned foul after a gas well was installed about 150 meters away. The well driller went deeper and deeper, in search of water free from any signs of petroleum. Suddenly, at a depth of 160 meters, the borehole began to rumble and natural gas burst out of the hole. It was several days before equipment was brought in to plug the wild borehole. Encana claimed that the driller had encountered a natural pocket of gas, but the EPA obtained the results of a test hole that had been drilled nearby in 1980—no gas had been detected within 300 meters of the surface.

More study needed

In the end, the report concludes that the available information "best supports an explanation that inorganic and organic constituents associated with hydraulic fracturing have contaminated ground water at and below the depth used for domestic water supply" and "gas production activities have likely enhanced gas migration at and below depths used for domestic water supply and to domestic wells in the area of investigation."

This does come with an important caveat: "further investigation would be needed to determine if organic compounds associated with hydraulic fracturing have migrated to domestic wells in the area of investigation." That's because "the existing data at this time do not establish a definitive link between deep and shallow contamination of the aquifer." Without wells of intermediate depth between the deep monitoring wells and shallower water samples, it's tough to firmly connect the two.

It's unclear whether similar contamination might have occurred in Pavillion if conventional methods of gas production had been used instead of hydraulic fracturing, but the chemicals used in fracking fluids do appear to present an additional risk.

The report echoes a US Department of Energy panel that called for the "collection of baseline data, greater transparency on chemical composition of hydraulic fracturing fluids, and greater emphasis on well construction and integrity requirements and testing."

The EPA's national review of fracking is currently still in progress, but the Pavillion investigation certainly figures to have an impact on its final conclusions. Until then, those with flammable tap water will continue to debate its causes—and should probably stock up on bottled water.